Study finds that people who inhaled two puffs of an oxytocin nasal spray were measurably more likely to risk all their money with a stranger, without consciously knowing why.

By Robert Lee Hotz, Times Staff Writer

The essence of trust — a catalyst of all friendship, trade and democracy — is a neurochemical that can be distilled in a nasal spray and used to ease the natural suspicion of strangers, researchers reported today.

The discovery is the first direct evidence that a hormone called oxytocin, which evolved 100 million years ago to aid mating among fish and breast feeding among mammals, also promotes trust between human beings, the scientists said.

The finding arises from a new wave of brain research designed to deconstruct how people make decisions, by investigating the neural impulses that dart beneath the surface of self-awareness.

In an experiment published in the current edition of the journal Nature, researchers at the University of Zurich in Switzerland and Claremont Graduate University determined that people who inhaled two puffs of an oxytocin nasal spray were measurably more likely to risk all their money with a stranger, without consciously knowing why.

"If I increase your level of oxytocin, I can induce you to overcome your anxiety in trusting a stranger," said Paul J. Zak, director of Claremont's center for neuroeconomic studies and a co-author of the research paper. "It is a [biochemical] signal we induce unknowingly all the time by looking people in the eye or shaking someone by the hand."

Although the researchers set up their experiment to test the effects of oxytocin on financial decisions, they believe the hormone is the keystone of a normal social life.

Trust is as crucial in love and diplomacy as in finance. Social phobias, which hinge on the inability to trust other people, are the third most common mental health problem.

"My conjecture is that it applies broadly to all kinds of social interactions where your trust could be abused," said economist Ernst Fehr in Zurich, the senior member of the research team.

The finding is an important advance in understanding the biology of human behavior, two independent experts said.

"Oxytocin enhanced trust," said University of Iowa neuroscientist Antonio Damasio. "The finding has powerful implications for understanding the brain. Remove trust and you compromise love, friendship, trade and leadership."

Dartmouth College neuroscientist Michael S. Gazzaniga, a member of the President's Council on Bioethics and author of "The Ethical Brain," said the researchers had laid "the foundation for a lot of new work on the human condition."

Researchers have long known that the hormone was important in the social behavior of animals.

Oxytocin also is active during human childbirth, when it enhances uterine contractions during labor and often may be administered to ease a difficult birth. For nursing mothers, it eases the production of breast milk.

Until now, its role in human social behavior had been a matter of conjecture.

To investigate its effects, the researchers set up an experiment in which investors could choose to risk money with strangers in a classic economics investment game. The investors had to decide how much to invest without knowing anything about their trading partners.

"We were trying to understand why people are so trusting with people they have never seen and will never see again," Zak said.

In all, 178 students from universities in Zurich volunteered.

Before launching into rounds of investment trading, they were given oxytocin or a placebo.

The oxytocin the researchers used for the experiment was in a hormone supplement once prescribed to women who had trouble breast-feeding. It is no longer sold in the United States.

The researchers found that the volunteers who took oxytocin were twice as likely to risk all their money with a stranger.

Overall, those who inhaled sprays of oxytocin invested 17% more than investors who received a placebo.

Moreover, the hormone only affected someone's response to another person. Those who engaged in financial trading with a computer partner showed no effect from the hormone, the scientists said.

At the least, the insight into the role of oxytocin suggests new ways to study and treat mental conditions in which people trust too readily, such as Williams syndrome, or are too suspicious, such as clinical paranoia, the two experts said.

Gazzaniga cautioned that it was too soon to know whether oxytocin would have the same decisive effect on human behavior outside the controlled conditions of a laboratory.

"I do wonder how it will play out in the human condition," he said. "A lot more work has to be done to really see it play out as a medication for social phobias. If it does work out, there all kinds of things for which it might be applicable."

The research also stirred misgivings about potential misuse by unscrupulous marketers or political operatives who might use oxytocin to prime a campaign crowd or set up a sales prospect.

"Every time you have any substance or behavior that could influence the way we act and our choices, one ought to be very alert," Damasio said. "This is the world of human nature. It is important for people to be aware and be attentive."

The researchers acknowledged the risk but dismissed such concerns on practical grounds.

The dose must be relatively large; any effect is temporary; and because the chemical quickly breaks down in the stomach, it must be administered by inhalation or injection, they said.

"There are quite severe limits on the ability to affect people involuntarily," said Fehr. "You would have to create a thick fog of oxytocin in the air to get an effect. It is difficult to imagine you could do this without people noticing."